This invention relates to high power coherent radiation sources and in particular to a continuously tunable free electron laser capable of generating high power pulses in the millimeter through submillimeter range.
State-of-the-art coherent radiation sources in the frequency range of interest (infrared, optical to ultraviolet) are typically molecular lasers which operate at fixed frequencies and are not widely tunable. Tunable dye lasers do exist, but these are limited in power since the dye will decompose by heating when the power becomes too large.
A recent development in high power coherent radiation sources is the free electron laser. A description of such a device is given in the periodical article First Operation of a Free Electron Laser, by D. A. G. Deacon et al., Physical Review Letter, April 1977, Volume 38, No. 16 PP892-894. The free electron laser of Deacon et al. is similar to the present invention in that it is widely tunable and does not contain a lasing medium which can be thermally damaged. However, it is driven by a low current electron beam from a linear accelerator and so is limited in peak power. The low current also limits the gain and efficiency of the device.
An improved apparatus and technique for providing tunable high power millimeter and submillimeter radiation utilizing free electron laser principles is disclosed by U.S. Pat. application Ser. No. 3,958,189 entitled Simulated Coherent Cyclotron Scattering, Millimeter, and Submillimeter Wave Generator issued to Phillip A. Sprangle et al. May 18, 1976. This device combines an optical cavity, an electromagnetic pump wave and an intense relativistic electron beam accelerator to achieve a tunable source of coherent radiation. However, because of the very powerful electromagnetic pump required by this device it is expensive and difficult to realize.
It is apparent from the foregoing review of the state-of-the-art that there currently exists the need for a coherent radiation source that is continuously and easily tunable, not limited in power, that has improved gain and efficiency and that can be easily and economically realized.
The present invention is directed toward satisfying that need.